FIG. 1, FIG. 2A, and FIG. 2B show, as a conventional example of the structure of a touch panel, the structure of a capacitive touch panel described in Japanese Patent Application Laid Open No. 2017-103317 (issued on Jun. 8, 2017). This touch panel has a structure in which a first conductive layer, an insulating layer, a second conductive layer, and a protective layer are sequentially laminated on a transparent base member 10. In FIG. 1, an area surrounded by a rectangular frame indicates a sensing area (sensor area) 20 where sensor electrodes are positioned. Details of the sensor electrodes are not shown in FIG. 1.
The sensor electrodes include a first sensor electrode and a second sensor electrode. The first sensor electrode is formed by the first conductive layer, and the second sensor electrode is formed by the second conductive layer.
As shown in FIG. 2A, the first sensor electrode 30 is configured such that a plurality of electrode rows 33 are arranged in rows along the Y direction, which is parallel to the short sides 22 of the sensing area 20, each of the plurality of electrode rows 33 being formed by connecting a plurality of island-shaped electrodes 31 arranged along the X direction, which is parallel to the long sides 21 of the sensing area 20, with connection sections 32.
As shown in FIG. 2B, the second sensor electrode 40 is configured such that a plurality of electrode rows 43 are arranged in rows along the X direction, each of the plurality of electrode rows 43 being formed by connecting a plurality of island-shaped electrodes 41 arranged along the Y direction, with connection sections 42.
The first sensor electrode 30 and the second sensor electrode 40 are individually made up of thin-line mesh. The electrode rows 33 and 43 intersect with each other in an insulated state. The connection sections 32 and 42 are positioned overlappingly.
Lead wiring lines 51 are drawn from both ends, in the X direction, of each of the electrode rows 33 of the first sensor electrode 30. Lead wiring lines 52 are drawn from one-side end, in the Y direction, of each of the electrode rows 43 of the second sensor electrode 40. Among the lead wiring lines 51 and 52 drawn from the sensing area 20 and arranged in rows, only those positioned at both ends are shown in FIG. 1, whereas the others are not shown.
Terminals 53 are formed and arranged at a middle portion along one long side of the base member 10, which is rectangular. The lead wiring lines 51 and 52 are extended to reach and connect to terminals 53. Ground wiring lines 54 are formed at a peripheral part of the base member 10 so as to surround the sensing area 20 and the lead wiring lines 51 and 52. The ground wiring lines 54 are also connected to terminals 53.
The lead wiring lines 51 and 52 and the terminals 53 are formed by the first conductive layer. The ground wiring lines 54 are formed by both the first and second conductive layers.
In this example, the first and second conductive layers, having the above-described structures, are formed by gravure offset printing by the use of electrically conductive ink that includes electrically conductive particles, such as silver particles.
In a touch panel having a sensing area that includes a conductive part made up of thin-line mesh and the conductive part is formed by gravure printing or gravure offset printing by using electrically conductive ink, as described above, blurring of the electrically conductive ink occurs at intersections of the thin-line mesh. Such blurring of the electrically conductive ink is visually recognized, affecting the visibility of a display unit in which the touch panel is arranged, thus reducing the visual quality of the touch panel.